.bg{
    width:100vw;
    height: 100vh;
    background-image: url('https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimages.uiiiuiii.com%2Fwp-content%2Fuploads%2F2018%2F03%2Fi-ui180325-1-5.jpg&refer=http%3A%2F%2Fimages.uiiiuiii.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1657791022&t=57ab2decf78ece42d160718e256c90e7');
}